1. Field of the Invention
The present invention relates to an information-recording apparatus, an information-recording method, an information-reproducing apparatus, an information-reproducing method, and an information-recording medium which are suitably applicable to a video recording and reproducing apparatus for home use or business use, for reproducing digital information from a tape recording medium.
2. Description of Related Art
In recent years, a video-reproducing apparatus for reproducing digital information such as video data and audio data from a tape recording medium has been often used as home use or business use. Such video-reproducing apparatus mounts a cassette having a magnetic tape wound around its reel. Eight reproducing magnetic heads (herein after, referred to as “reproducing heads”) reproduce video data and audio data that has recorded in a magnetic tape. Video data and audio data are recorded in the magnetic tape according to a predetermined recording format (herein after, referred to as “VTR format”).
FIG. 1 is a view for showing an example of a conventional VTR footprint in which a video sync (M) and an audio sync (N) coexist. The conventional VTR footprint (ECC configuration and data recording format) shown in FIG. 1 is provided as a format recorded by a helical recording head (not shown). In 12 tracks of the footprint shown in FIG. 1, a video sync (sync (M)) is allocated to an upper position of a magnetic tape 80. In this video sync (M), 36 ECC blocks (data in units of encoding) from table 0 to table 35 are recorded.
In addition, a video sync (M) is allocated to a lower position of the magnetic tape 80 shown in FIG. 1. In this video sync (M), 36 ECC blocks (data in units of encoding) from table 0 to table 35 are recorded. The size of each of the video syncs (M) of the upper and lower positions is 12 tracks×189 bytes. An audio sync (N) is allocated between the video syncs (M) of the upper and lower positions, and audio data Da is recorded therein. The audio sync (N) is segmented into eight segments, and the size of one segment is 4 bytes×12 tracks.
Here, assuming that a recording head is scanned from a side of the video sync (M) of a lower position to a side of the video sync (M) of upper position, items of audio data A1, A9, and A5 are allocated to a first segment; items of audio data A2, A10, and A6 are allocated to a second segment; items of audio data A3, A11, and A7 are allocated to a third segment; items of audio data A4, A12, and A8 are allocated to a fourth segment; items of audio data A5, A1, and A9 are allocated to a fifth segment; items of audio data A6, A2, and A10 are allocated to a sixth segment; items of audio data A7, A3, and A11 are allocated to a seventh segment; and items of audio data A8, A4, and A12 are allocated to an eighth segment, respectively.
In addition, a gap Gav is allocated between the video sync (M) of upper position and an audio sync (N) of the eighth segment. A gap Gaa is allocated between audio syncs of each segment. A servo pilot (servo control signal: CTL signal) is allocated between an audio sync (N) of the fourth segment and an audio sync (N) of the fifth segment. A gap Gs1 is allocated between this servo pilot and an audio sync (N) of the fourth segment and a gap Gs2 is allocated between the servo pilot and an audio sync (N) of the fifth segment. A gap Gva is allocated between an audio sync (N) of the first segment and the video sync (M) of the lower position. This is because a signal processing space is allocated during reproduction.
In the meantime, in a VTR format in which two types of sync lengths exist, as described above, in addition to the above edit gaps, there is a need for providing a space for signal processing between a video sync (M) and an audio sync (N), which is required for carrying out C1 correction processing. This principle is shown in FIG. 2. FIGS. 2A and 2B are timing charts each showing an example of MN switching in a C1-correcting circuit.
In general, C1 correction processing requires a delay according to a sync length. This delay can be expressed in a form such that a sync length and a length of its C1 parity are multiplied by a coefficient. In actuality, this coefficient is different depending on the C1-correcting circuit. In examples shown in FIG. 2A and FIG. 2B, however, both of the coefficients relevant to a sync length and a parity are defined as 2.
FIG. 2A shows a case in which a gap Gva at a portion moving a video sync (M) to an audio sync (N) is sufficiently long. The gap Gva is set between the video sync (M) and the audio sync (N) in a current data string. Here, a delay according to parity calculation relevant to a sync length M is defined as P1, and a delay according to parity calculation relevant to a sync length N is defined as P2.
A delay of C1 correction processing relevant to this sync length N is shorter than that relevant to a video sync (M). However, since the gap Gva is sufficiently long, the video sync (M) and the audio sync (N) in the next data string do not collide with each other at an output of the C1-correcting circuit. Namely, even if a processing time of (M+P1)×2 is taken for C1 correction processing according to the video sync (M), the gap Gva is set to be sufficiently long. Thus, C1 correction processing according to the audio sync (N) in the next data string can be carried out after an elapse of time of (M+P2)×2 from a time point when the audio sync (N) of the current data string is input to the C1-correcting circuit, following an input of the video sync (M) of the current data string.
FIG. 2B shows a case in which a gap Gva−1 at a portion moving from a video sync (M) to an audio sync (N) is shorter than the above gap Gva. The gap Gva−1 is set between the video sync (M) and the audio sync (N) in a current data string. A delay of C1 correction processing relevant to this sync length N is also shorter than that relevant to the video sync (M). Thus, since the gap Gva′ is not sufficient, the video sync (M) and the audio sync (N) in the next data string collide with each other at an output of the C1-correcting circuit.
In the meantime, according to a VTR footprint of the conventional style, the following problems arise.
(1) A servo pilot is allocated in the middle of a recording track of the magnetic tape 80 shown in FIG. 1. The audio syncs (N) are allocated in front of or at the rear of the servo pilot. Further, the video syncs (M) are allocated in front of or at the rear of the audio syncs. Therefore, this allocation causes waveform reduction relevant to an effective track length limited in the magnetic tape 80.
(2) In addition, C1 correction processing according to a video sync (M) is carried out at a portion moving from the video sync (M) to an audio sync (N) shown in FIG. 2B, namely, by taking a processing time of (M+P1)×2. However, since a gap Gva−1 is not set to be sufficiently long, the C1 correction processing according to the audio sync (N) of next data string is carried out after an elapse of time of (M+P2)×2 from a time point when the audio sync (N) of current data string is input to the C1-correcting circuit, following an input of the video sync (M) of the current data string. As a result, the back of the video sync (M) of the next data string is overtaken by the audio sync (N) of the next data string, and thus, the data is destroyed.
The present invention has been made in order to solve the foregoing problems. It is an object of the present invention to provide an information-recording apparatus, an information-recording method, an information-reproducing apparatus, an information-reproducing method, and an information-recording medium, which are capable of utilizing a gap portion between the recording portions of digital information having different information-recording lengths and a recording portion of a servo control signal as a signal processing space required for carrying out error correction processing such as C1 correction processing during reproduction of digital information.